Signaling agent realizing method based on media gateway control protocol

FIELD OF THE INVENTION

The present invention relates to a field of communication technology, specifically relates to a method for realizing signalling agent function with a media gateway control protocol.

BACKGROUND

Media Gateway Control Protocol (MGCP), is RFC2705 Protocol of the Internet Engineering Task Force (IETF), and Media Gateway Control (MEGACO) is RFC 3015 Protocol of IETF. Media Gateway Control Protocol (MGCP/MEGACO) is a protocol between soft switch equipment and media gateway for controlling action of media gateway.

With an idea of discomposing gateways, MEGACO/MGCP protocol discomposes original gateways processing signalling and media stream into two parts: media gateway (MG) and media gateway control (MGC). A physical logic entity on MG can be identified with endpoints, as shown in <figref idrefs="DRAWINGS">FIG. 1</figref>. A MGC controls action of a MG through MEGACO/MGCP Protocol, and processes requests submitted by a MG; a MG mainly processes information of media stream. Both MGC and MG are network elements in a network, and communicate with each other through MEGACO/MGCP Protocol.

Due to decomposition of MGC and MG, a MGC can control action of multiple MGs, and sometimes such situation may happen that a MGC and MGs controlled by it locate in different networks and thus an agent equipment is needed to realize signalling agent for MGC's controlling on MGs.

A signalling agent means to realize, by a signalling agent, traversing MGCP/MEGACO signalling and media stream controlled through networks, where MGC and MGs are in different networks and can not be reachable to one another by routes, so as to make MGC enable to control MGs in other networks completing call establishing and media stream intercommunicating.

Agent equipment is independent equipment, which provides signalling and media stream agent function among networks in a packet switching network and takes charge of providing signalling and media stream agent between different networks and network address translation.

At present, a common method for realizing signalling agent among different networks is based on network address translation (NAT), but in this method agent equipment cannot make MGC entirely transparent, and complexity for realizing call services on MGC is increased; meanwhile detailed information on corresponding MG needs to be configured on the agent equipment, and, thus, any change on MG under control of MGC requires informing the agent equipment to change configuration, which increases operation maintenance cost.

SUMMARY OF THE INVENTION

In the present invention, a technical problem to be solved is to provide a method for realizing signalling agent based on media gateway control protocol to overcome shortcomings in the prior art, to implement transparent traversing of MGCP/MEGACO protocol among different networks, to make MGC not concern network location of MGs, and to decrease operation maintenance cost.

The method for realizing signalling agent based on media gateway control protocol provided by the present invention comprises the following steps of:

providing agent equipments among media gateways and a media gateway controller located in different networks, the agent equipment providing signalling agent and network address translation function among different networks;

requesting for registering a media gateway in the media gateway controller;

if a MGCP/MEGACO signalling between a media gateway and the media gateway controller is not related to media, directly replacing transaction number on the agent equipment and then forwarding; if a MGCP/MEGACO signalling is related to media, processing media attribute correspondingly by the agent equipment and then forwarding.

All media gateways under same media gateway controller have different domain names, every endpoint includes domain name information of the media gateway, and the media gateway controller can distinguishes media gateways according to their domain names in endpoint identifiers.

The step of registering media gateways in the media gateway controller further comprises.

sending a register request message from a media gateway to the media gateway controller, recording message identifier of the media gateway received by the agent equipment to generate a piece of information about this media gateway;

assigning a new transaction number by the agent equipment to the register request message to replace original transaction number in the register request message, recording the media gateway sending the request, and then forwarding the register request message to the media gateway controller;

sending a register response message to the media gateway from the media gateway controller after the media gateway registers successfully;

determining the media gateway by the agent equipment according to the new transaction number in the register response message, replacing the new transaction number with original transaction number, and forwarding the register response message to corresponding media gateway.

The step of replacing the transaction number by the agent equipment further comprises:

assigning a new transaction number to each of the request message registers sent from the media gateway to the media gateway controller, by the agent equipment, and recording the media gateway sending the request message;

finding corresponding media gateway by the agent equipment according to the new transaction number reassigned, after receiving the response message to the request message sent by the media gateway controller, replacing the new transaction number in the response message with original transaction number, and then forwarding the response message to corresponding media gateway;

sending a request message, sent from the media gateway controller to a media gateway, to corresponding media gateway by the agent equipment according to domain name in endpoint identifier.

The step of processing a MGCP/MEGACO signalling related to media by the agent equipment further comprises:

creating or modifying corresponding media forwarding port and forwarding table on the agent equipment after receiving a creating or modifying connection signalling sent from the media gateway controller to a media gateway;

replacing related media information in the signalling with corresponding network address information of the media forwarding port on the agent equipment, and forwarding the signalling to corresponding media gateway;

if the signalling is a signalling for creating a connection, recording endpoint identifier of the connection on the agent equipment;

modifying forwarding table of corresponding media forwarding port by the agent equipment according to a response signalling when the media gateway sends the response signalling related to media to the media gateway controller;

replacing media information in the response signalling on the agent equipment with network address information of corresponding media port, and then sending to the media gateway controller;

sending a release connection signalling to the media gateway from the media gateway controller after calling finishes, releasing corresponding media forwarding port by the agent equipment according to endpoint identifier, and then forwarding the signalling to corresponding media gateway.

The method of the present invention requires no configuration on any information about media gateways based on MGCP/MEGACO protocol, and the media gateways can directly be controlled by the media gateway controller. Thus, the media gateway controller does not concern with whether media gateways are in same network or not, which facilitates services realized on the media gateway controller. Meanwhile, any change on service control on the media gateway needs only perform on the media gateway controller, but not modify on the agent equipment, thus user management is highly facilitated. Furthermore according to the present invention multiple agent equipments may be used for implementing the media gateway traversing through more networks for multiple times.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic diagram of a system adopting MGCP/MEGACO protocol;

<figref idrefs="DRAWINGS">FIG. 2</figref> is a schematic diagram of an embodiment of a system adopting MGCP/MEGACO protocol;

<figref idrefs="DRAWINGS">FIG. 3</figref> is a flow chart for realizing MGCP/MEGACO information agent according to the present invention;

<figref idrefs="DRAWINGS">FIG. 4</figref> is a schematic diagram for dynamically generating MG information on the agent equipment according to the present invention;

<figref idrefs="DRAWINGS">FIG. 5</figref> is a flow chart of a registering process from a media gateway to a media gateway controller; and

<figref idrefs="DRAWINGS">FIG. 6</figref> is a flow chart of a process for forwarding media stream through networks by signalling agent according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be further described in details in a combination with attached drawings and embodiments below.

<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic diagram of a system in the prior art, which is already introduced in background and will not repeat here.

In a schematic diagram of a system realizing MGCP/MEGACO signalling agent according to the present invention as shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, a media gateway controller MGC and a media gateway MG<b>3</b> locate in network <b>1</b>, media gateways MG<b>1</b> and MG<b>2</b> locate in network <b>2</b>, and the media gateway controller controls media gateways MG<b>1</b>, MG<b>2</b> and MG<b>3</b> by MGCP/MEGACO protocol.

According to the method provided by present invention, an agent equipment is provided between MGC and MG<b>1</b>, MG<b>2</b> that are not in same network, that is an agent equipment between network <b>1</b> and network <b>2</b>. All MGs under control of same MGC have different domain names, and MGC distinguishes uniquely each MG by its domain name in endpoint identifier.

The agent equipment has at least two network addresses; one is address BIP<b>1</b> in network <b>1</b> where MGC locates, the other one is address BIP<b>2</b> in network <b>2</b> where MG<b>1</b> and MG<b>21</b> locate. IP addresses and port of MGC configured on MG<b>1</b> and MG<b>2</b> are address BIP<b>2</b> and port P<b>2</b> of the agent equipment; and MGC distinguishes MGs by their domain names.

<figref idrefs="DRAWINGS">FIG. 3</figref> is a flow chart for realizing MGCP/MEGACO information agent on the agent equipment according to the present invention, firstly, an agent equipment is provided between MG and MGC in different networks, and provides signalling agent and network address translation functions among different networks. Then MG registers to MGC, after registering successfully, for a MGCP signalling between MGC and MG that is not related to media, the agent equipment directly replaces transaction number and then forwards; for a MGCP signalling that is related to media, the agent equipment processes media identifier correspondingly and then forwards.

<figref idrefs="DRAWINGS">FIG. 4</figref> and <figref idrefs="DRAWINGS">FIG. 5</figref> show processes of requesting for registering MG. in MGC;

Step <b>301</b>: MG sends a RSIP message to MGC for registering, in which its transaction number is TransID, Agent equipment receives the message on address BIP<b>2</b> and port P<b>2</b> and records attributes such as source address and port number of MG message received and domain name of MG, to generate a piece of information about the MG;

Step <b>302</b>: The agent equipment reassigns a transaction number TransID′ to the registering message, replaces original transaction number TransID in the registering message with it, records corresponding relation of TransID and TransID′, and then forwards the registering message to MGC from BIP<b>1</b> address;

Step <b>303</b>: MGC registers MG successfully according to its domain name, and then sends a response message to MG;

Step <b>304</b>: After receiving the response message returned by MGC from address BIP<b>1</b>, the agent equipment finds corresponding record according to the transaction number TransID′ in the response message, obtains MG sending the registering message and its original transaction number TransID, replaces the transaction number TransID′ in the response message with TransID, and forwards to corresponding MG from address BIP<b>2</b>.

After receiving each of request messages sent to MGC by MG, the agent equipment reassigns a new transaction number to the request message, replaces original transaction number with the new transaction number, and then records MG sending the request. After receiving a response message returned by MGC for the request message, the agent equipment finds corresponding MG according to the reassigned new transaction number, replaces the new transaction number in the response message with the original transaction number, and then forwards the response message to corresponding MG. For a request message sent to MG by MGC, the agent equipment forwards to corresponding MG according to domain name contained in the endpoint identifier.

<figref idrefs="DRAWINGS">FIG. 6</figref> represents a process for forwarding media stream over networks realized by MGCP signalling agent through the agent equipment.

Step <b>401</b>: MGC send MG a signalling CRCX for establishing a connection port on MG, the agent equipment analyzes the signalling, then knows that the signalling is related to media, and establishes a corresponding media forwarding port A′ on the agent equipment; if the signalling CRCX has remote connection attribute, a media forwarding table is established on the media forwarding port A′ with IP and port in the signalling, and IP and port in the signalling is modified into address BIP<b>2</b> and Port A′ on the agent equipment; meanwhile, name for endpoint identifier of connection to be established by MG is recorded.

Step <b>402</b>: The agent equipment forwards MG the CRCX signalling with modified remote connection attribute;

Step <b>403</b>: after creating the connection port successfully according to the signalling, MG sends a response message for CRCX signalling, the agent equipment receives the response message, then modifies media forwarding table on port A′ with IP and port in local connection attribute of the response message, and replaces IP and port in local connection attribute of the response message with address BIP<b>1</b> and port A′;

Step <b>404</b>: the agent equipment forwards MGC the response message for CRCX with modified local connection attribute;

Step <b>405</b>: MGC sends MG a MDCX signalling for modifying a connection port on MG, and the agent equipment finds media forwarding port A′ according to endpoint identifier of MG connection recorded, then modifies media forwarding table on port A′ with IP and port in remote connection attribute of the MDCX signalling, and modifies IP and port in the MDCX signalling with BIP<b>2</b> and port A′;

Step <b>406</b>: the agent equipment forwards MG the MDCX signalling with modified remote connection attribute;

Step <b>407</b>: MG returns a response message for modifying connection successfully;

Step <b>408</b>: the agent equipment forwards the response message to MGC;

Step <b>409</b>: after the call ends, MGC sends MG a DLCX signalling for releasing connection, and the agent equipment finds corresponding media forwarding port A′ according to endpoint identifier, and releases media forwarding port A′;

Step <b>410</b>: the agent equipment forwards the DLCX message to MG;

Step <b>411</b>: MG releases connection according to the signalling, and after done successfully replies to MGC; and

Step <b>412</b>: the agent equipment forwards MGC the reply to the signalling.

If MG needs traverse through multiple networks for multiple times, multiple agent equipments may be used for realization.

It should be noted that the embodiments above are only for describing the solutions of the present invention but not for limiting. Although the present invention is described with embodiments, an ordinary person skilled in the art should understand that various modifications and variations may be made in the present invention without departing from the spirit or scope of the invention, which all should be covered within the scope of the appended claims of the present invention.